I want to start out by saying that this is not a homework problem, this is something I'm trying to figure out for thesis work. If that should go in the homework problem section, I will gladly post there. A certain mass model I'm working with (Bissant & Gerhard) has a particularly gross form. exp(-(r'/rc)^2)*(1+r'/r0)^-α Separating out constants and rearranging, I can massage it into this form: λ^n*exp(-x^2)*(λ+x)^-n , where λ is constant and n is known (1.8 for those who want to know) My problem is now I have to integrate this sucker, and I've never been particularly good at parts. I did find a guide and I was able to walk myself through it, however, my issue come here. I separated it out as: u=(λ+x)^-n, du=-n(λ+x)^(-n-1)dx dv=exp(-x^2), v= <-- PROBLEM Unless I integrate dv from 0 to infinity, the gaussian is sqrt(pi)/2 times an error function, which is useless to me. So... Can I integrate the dv from 0 to infinity and set different limits to the subsequent integrals? i.e., can I have dv=exp(-x^2), v=sqrt(pi)/2, but when it comes to the uv-∫vdu, can I set that integral from 0 to some finite limit? Any help is much appreciated, and as I said before, if this is better suited for another board, I will gladly post there.